1. Field of the Invention
The present invention relates to a network system comprising a gateway apparatus for connecting a wide area network and a local area network (to be referred to as a LAN hereinafter), and a management method therefor.
2. Description of the Prior Art
Communication terminals such as facsimile apparatuses arranged at geographically remote locations like the main and branch offices of a certain company are normally connected through a wide area network 1, as shown in FIG. 12.
In FIG. 12, reference numeral 1 denotes the wide area network such as a telephone network or a digital network; 2, denotes a communication terminal apparatus arranged at the head office; and 3, 4, and 5, denote communication terminal apparatuses arranged at branch offices.
When the size of one office is relatively large and a plurality of communication terminal apparatuses are arranged in one office, the arrangement shown in FIG. 13 is advantageous.
In the arrangement shown in FIG. 13, a plurality of (e.g., three) communication terminal apparatuses 3-1, 3-2, and 3-3 are assumed to be arranged in a single office. Communication is performed inside the office using these communication terminal apparatuses through terminal adapters 8-1, 8-2, and 8-3, and a LAN 6. Communication is performed with other communication terminal apparatuses outside the office, e.g., communication terminal apparatuses 2, 4, 5, and the like through a gateway apparatus 7 and a wide area network 1.
This system utilizes the LAN 6 which allows high-speed communication and does not incur high communication costs for intra-office communication having a high communication frequency, and uses the wide area network 1 only in a communication with an apparatus outside the office. Thus, this system is a rational one.
However, the above-mentioned conventional network system has the following drawbacks.
(1) When the communication terminal apparatuses 2 to 5 are directly connected to the wide area network 1, as shown in FIG. 12, location of a source of an error when a communication error occurs is relatively easy since it can be performed by determining whether the error occurred at the wide area network 1 side or at the terminal side of the system.
However, in the network system including the LAN shown in FIG. 13, errors can also occur in the gateway apparatus 7, the LAN transmission path 6, and terminal adapters 8, and the like.
In this case, when an error occurs, determining its location requires an examination of each type of apparatus in the system, resulting in much labor and time.
(2) In a system required to have high reliability, in order to eliminate the drawback (1) and to allow quick location of a source or an error, a LAN monitoring apparatus is separately connected.
In general, a LAN monitoring apparatus of this type is a special apparatus, and is expensive, thus impairing the economic advantages of the system.